Exposure apparatus and device manufacturing method

ABSTRACT

A method of exposing a substrate to a pattern using an exposure apparatus. The method includes performing an update of a parameter, necessary for processing in the exposure apparatus, through measurement, in which the measurement is performed for each update of the parameter, setting a validity period for the updated parameter, in which the validity period represents a period in which the updated parameter is valid for the processing, predicting a completion time for a next exposure processing segment to be performed by the exposure apparatus, determining whether the predicted completion time is after expiration of the validity period, in which the setting of the validity period is performed after the performing of the update and before the determining step, and causing the update of the parameter to be performed if it is determined in the determining step that the predicted completion time is after the expiration of the validity period.

This application is a divisional application of copending U.S. patentapplication Ser. No. 10/969,072, filed Oct. 21, 2004.

FIELD OF THE INVENTION

The present invention relates to an exposure technique for manufacturingmicro devices, including a semiconductor device, such as an IC or anLSI, a liquid crystal substrate, a CCD, and a thin film magnetic head.

BACKGROUND OF THE INVENTION

Conventionally, in a process of fabricating a semiconductor with anultra fine pattern, such as an LSI or a VLSI, a reduced projectionexposure apparatus (hereinbelow, simply referred to as an “exposureapparatus”), which reduction-exposes a substrate coated with aphotosensitive material to a circuit pattern drawn on a mask, therebyprint-forming the pattern, is employed. In accordance with an increasein packaging density, further microminiaturization of a pattern isrequired, and handling such a pattern is required in the exposureapparatus.

To form an ultra fine pattern with the exposure apparatus, it isnecessary to maintain high processing accuracy, such as focus accuracy,to bring an image formation surface (focus surface) of a reducedprojection lens into correspondence with a subject (wafer) surface andan alignment accuracy for alignment of respective patterns throughplural process steps. For this purpose, in the exposure apparatus,adjustable correction parameters are measured and set prior to substrate(wafer) exposure processing, and apparatus running is performed whilethe organized constituent elements (units) are controlled based on theparameters.

However, even when the correction parameters have been previouslyadjusted based on measurement, proper values (true values) of thecorrection parameters vary with an elapse of time, due to vibrationduring apparatus running, environmental change in atmospheric pressure,temperature, and the like, and thermal factors, such as exposure heat,and the like. That is, the correction parameters move away from theproper values. Accordingly, it is necessary to appropriately correct thecorrection parameter values by the amounts of fluctuation in therespective constituent elements.

Next, a conventional correction method for running control will bedescribed. Prior to exposure of a substrate (wafer) by an exposureapparatus, an operator sets a recipe (operation parameters) for theexposure apparatus in accordance with a semiconductor device circuitpattern. The exposure apparatus sequentially performs exposureprocessing on the substrates (wafers), while controlling theconstituents (units) in accordance with the recipe. FIG. 5 shows anexample of a time chart of substrate (wafer) exposure by the exposureapparatus. In the figure, the lateral axis represents time, and arectangular block, a brief segment of processing. In this example, whilea substrate (wafer) is repeatedly exposed, the amount of fluctuation ofan image formation surface position of a projection lens from a designedvalue (correction parameter) due to exposure heat of illumination on thereduced projection lens, or the like, is measured, and the imageformation surface position is corrected by a predetermined number ofwafers (three in FIG. 5).

When production by the exposure apparatus is started based on the recipeto measure the fluctuation of the image formation surface position ofthe projection lens (correction parameter) and corrects the position bythree substrates (wafers), the fluctuation of the image formationsurface position of the projection lens is measured prior to exposure ofa first substrate (wafer), and the fluctuation-adjustable constituentelements (units) are properly controlled in accordance with thecorrection value. Next, substrate (wafer) exposure processing isrepeated for three wafers, and again, the fluctuation of the imageformation surface position of the projection lens is measured andcorrection is performed. Hereinafter, the measurement and correction arerepeated by processing for three wafers. Thereby, the processingaccuracy of the apparatus is maintained (for example, see JapanesePatent No. 3218631, paragraph 0063, which matured from Japanese PatentLaid-Open No. 5-021319).

In accordance with the development of recent ultra micro devices, theexposure apparatus must maintain higher accuracy. Today, severalhundreds of correction parameters are known, and further, the number ofcorrection parameters is increased for maintaining the apparatusaccuracy. Further, allowable fluctuation amounts of the respectivecorrection values are increasingly severe.

In this situation, in a case wherein the correction timing of thecorrection parameter is set with a predetermined number of wafers, as inthe above-described conventional art, the difference between thecorrection parameter and a proper value might exceed a threshold valueduring wafer processing. In such a case, the quality of exposure in thewafer cannot be ensured, and the yield is degraded.

Further, the increase in the number of correction parameters increasesthe time required for measurement and correction of the parameters. Asthe fluctuation amounts become stricter, the measurement and correctionphase must be repeated in a short period, and thus, the productivity ofthe exposure apparatus is degraded. Accordingly, it is important toprevent degradation of productivity of the exposure apparatus whilemaintaining accuracy of correction parameters. Further, to previouslydetermine a correction period (correction timing) for each of thecorrection parameters by an operator, as in the above-describedconventional art, requires a lot of time and effort.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the aboveproblems, and has its object to suppress unnecessary degradation ofproductivity in exposure processing while retaining necessary exposureaccuracy.

According to one aspect of the present invention, there is provided anexposure apparatus for exposing a subject to a pattern, comprising anupdate system to update a parameter necessary for processing in theexposure apparatus through measurement, a setting system to set avalidity period of the parameter updated by the update system, and acontrol system to cause the update system to perform an update based onthe validity period.

Further, in a device fabrication method according to the presentinvention, a device is fabricated by using the above-described exposureapparatus.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame name or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a block diagram schematically showing the construction of anexposure apparatus according to a first embodiment of the presentinvention;

FIG. 2 is an explanatory view of exposure processing by the exposureapparatus in FIG. 1;

FIG. 3 is an explanatory view of reflected light when a referencereflecting mirror and an image surface of a projection lens are incorrespondence with each other, in the exposure apparatus according tothe first embodiment;

FIG. 4 is an explanatory view of reflected light when the referencereflecting mirror and the image surface of the projection lens are notin correspondence with each other, in the exposure apparatus accordingto the first embodiment;

FIG. 5 is a timing chart showing the conventional apparatus correctionoperation;

FIGS. 6A to 6C are timing charts showing an apparatus correctionoperation according to the first embodiment;

FIGS. 7A to 7C are timing charts showing the apparatus correctionoperation according to a second embodiment of the present invention;

FIGS. 8A to 8C are timing charts showing setting of a correction valuevalidity period according to a third embodiment of the presentinvention;

FIG. 9 is a flowchart showing the apparatus correction operationaccording to the first embodiment;

FIG. 10 is a flowchart showing the apparatus correction operationaccording to the second embodiment; and

FIG. 11 is a flowchart showing the flow of an entire semiconductordevice fabrication process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

<First Embodiment>

FIG. 1 is a block diagram schematically showing the construction of astep-and-scan type exposure apparatus according to a first embodiment ofthe present invention. In FIG. 1, reference numeral 101 denotes a pulselaser light source, filled with gas, such as KrF, to emit laser light.The pulse laser light source 101 emits light with a wavelength of 248 nmin a far ultraviolet area. Further, the pulse laser light source 101 isprovided with a front mirror as a resonance unit, a diffraction gratingto narrow the band of the exposure wavelength, a narrow-band moduleincluding a prism, a monitor module including a spectroscope, adetector, and the like, for monitoring stability of the wavelength andspectral bandwidth, a shutter, and the like (all not shown). A lasercontroller 102 performs control for a gas exchange operation in thepulse laser light source 101 and control for wavelength stabilization,control of discharged/applied voltage, and the like. In the firstembodiment, the laser controller 102 does not perform controls only byitself, but the controls are performed in accordance with commands froma main controller 103, which controls the overall exposure apparatusconnected with an interface cable.

A beam emitted from the pulse laser light source 101 is shaped to apredetermined beam shape via a beam shaping optical system (not shown)of an illumination optical system 104, and inputted into an opticalintegrator (not shown). The optical integrator has a large number ofsecondary light sources to irradiate a mask 109, to be described later,with a uniform illumination distribution. The shape of opening aperture105 of the illumination optical system 104 is an approximately circularshape, and the diameter of the opening, by extension, the aperturenumber (NA) of the illumination optical system, can be set to a desiredvalue by an illumination system controller 108. In this case, the valueof the ratio of the opening number of the illumination optical system tothe opening number of a reduction projection lens 10 to be describedlater is a coherence factor (σ value), and the illumination systemcontroller 108 controls the opening aperture 105 of the illuminationsystem to thereby set the σ value. A half mirror 106 is provided on theoptical path of the illumination optical system 104, and a part ofexposure light to irradiate the mask 109 is reflected and extracted withthe half mirror. A photo sensor 107 for ultraviolet light is provided onthe optical path of the reflected light from the half mirror 106, togenerate an output corresponding to the intensity of exposure light(exposure energy). The output from the photo sensor 107 is converted toexposure energy per one pulse by an integrating circuit (not shown) forintegration by pulse light emission in the pulse laser light source 101,and inputted via the illumination system controller 108 into the maincontroller 103, which controls the overall exposure apparatus.

The reticle (or mask) 109 where a semiconductor device circuit patternto be printed is formed, is irradiated with exposure light from theillumination optical system 104. As a variable blind (not shown), alight shielding plate is provided in a plane in an orthogonal directionto the optical axis, to arbitrarily set an irradiation area of thecircuit pattern surface of the mask 109. FIG. 2 shows a status where themask 109 is irradiated. A part of a circuit pattern 202 on the mask 109is slit-irradiated with a slit light flux 203, and reduction-exposure ofthe part of the circuit pattern 202 is made on a wafer 115 coated with aphoto resist at a reduction scale β (β is, e.g., ¼) with a projectionlens 110 shown in FIG. 1. At this time, as in an arrow (Scan) in FIG. 1,multiple pulse exposure from the pulse laser light source 101 isrepeated while the mask 109 and the wafer 115 are scanned in mutuallyopposite directions to the projection lens 110 and the slit light flux203 at the same speed rate corresponding to the reduction scale β of theprojection lens 110. In this manner, the entire circuit pattern 202 onthe mask 109 is transferred to one or plural chip areas on the wafer115.

An opening aperture 111 of the projection lens 110 having anapproximately circular opening shape is provided on the pupil surface(Fourier transform surface to the reticle) of the projection lens 110.The diameter of the opening is controlled by a driving unit 112, such asa motor, thereby, a desired aperture value is set. Further, a field lensdriving unit 113 moves a field forming a part of the lens system of theprojection lens 110 in the optical axis direction of the projection lensby utilizing air pressure or a piezoelectric device, which excellentlymaintains the projection scale and distortion error while preventingdegradation of various aberrations of the projection lens.

A wafer stage 116, which is movable in three-dimensional directions,moves in the optical axis direction (z direction) of the projection lens110 and in a plane orthogonal to the direction (X-Y plane). A laserinterferometer 118 measures the distance to a moving mirror 117 fixed onthe wafer stage 116, thereby detecting the X-Y surface position of thewafer stage 116. A wafer stage controller 12 under the control of themain controller 103 of the exposure apparatus detects the position ofthe wafer stage 116 by the laser interferometer 118, and controls adriving unit 119 such as a motor, thereby moving the wafer stage 116 toa predetermined X-Y plane position.

In the present embodiment, a so-called step-and-scan method is employed.That is, when positioning of the mask 109 and the wafer 115 has beenperformed to set them in a predetermined relation, the laser controller102, the wafer stage controller 120 and a mask stage controller 124perform control for scan exposure to transfer the entire circuit pattern202 on the mask 203 to the chip area(s) on the wafer 115, based on asynchronizing signal from the main controller 103. Thereafter, the wafer115 is moved in the X-Y plane by a predetermined amount with the waferstage 116, and similarly, projection exposure is sequentially performedon the other areas of the wafer 115.

Next, a so-called through-the-lens auto focus system (TTLAF) will bedescribed with reference to FIGS. 3 and 4. The system detects a focusposition change of the projection lens as an example of the correctionparameters by detecting a focused point through the projection lens 110.In FIGS. 3 and 4, a focus mark 303 is formed with a light transmittingmember 301 and a light shielding member 302 on the mask 109. First, FIG.3 shows a status where a reference plane mirror 304 is in the focusposition of the projection lens 110. Light passed through the lighttransmitting member 301 on the mask 109 is gathered via the projectionlens 110 on the plane mirror 304 and reflected. The reflected lightmoves in the same optical path as that upon approach to the mirror, thenis gathered via the projection lens 110 on the mask 109, and passesthrough the light transmitting member 301 on the mask 109. At this time,the measurement light is not eclipsed with the light shielding member302, but all the light flux passes through the light transmitting member301.

On the other hand, FIG. 4 shows a status where the reference planemirror 304 is shifted from the focus position of the projection lens110. The light passed through the light transmitting member 301 arrivesat the reference plane mirror 304 via the projection lens 110. However,as the reference plane mirror 304 is not in the focus surface of theprojection lens 110, the measurement light, as spreading light flux, isreflected by the reference plane mirror 304. The reflected light movesin an optical path different from that upon approach to the mirror, thenpasses through the projection lens 110, and arrives at the mask 109 as alight flux having a spread corresponding to the amount of shift of thereference plane mirror 304 from the focus surface of the projection lens110, without being gathered on the mask 109. At this time, a part of thelight flux is eclipsed with the light shielding member 302 on the mask109, and all the light flux cannot pass through the light transmittingmember 301. That is, the amount of reflected light through the mask 109when the reference plane mirror 304 corresponds with the focus surfaceis different from that when the reference plane mirror 304 does notcorrespond with the focus surface.

To detect the focus position (image surface position) of the projectionlens 110, the reference plane mirror 304 attached to the wafer stage 116is moved to a position immediately below the projection lens 110 inadvance. Next, the reference plane mirror 304 is step-driven in theoptical axis direction of the projection lens 110, then the referenceplane mirror 304 is irradiated and reflected light is measured by aTTLAF system (not shown). Thus, a reflected light amount profile isobtained by repeating the step driving and measurement of reflectedlight, and the focus position (image surface position) is detected.

Next, management of the correction parameter, in the exposure apparatushaving the above construction, will be described below.

First, a particular control method for automatically planning timing ofmeasurement and correction of a correction parameter will be describedwith reference to the timing charts of FIGS. 6A to 6C and the flowchartof FIG. 9. FIGS. 6A to 6C schematically show the sequence of waferexposure processing and apparatus correction. In the apparatuscorrection in the present embodiment, the above-described focus position(hereinbelow, image surface correction value) of the projection lens ismeasured as a correction parameter.

When production by the exposure apparatus is started, measurement of theimage surface correction value is performed prior to wafer exposureprocessing (step S11 in FIG. 9 and step S601 in FIG. 6A). A fluctuationamount from an optimum value (designed value) is obtained as an imagesurface correction parameter, and the field lens driving unit 113 andthe wafer stage control unit 119 as constituent elements (units) arecorrection-controlled based on the parameter. After the correctioncontrol, a validity period (Ts) is set for the image surface correctionparameter, and measurement of an elapsed time (Tr) from the imagesurface correction is started (step S12). Note that the validity period(Ts) is a parameter representing a period where correction using themeasured correction value is possible (e.g., a period wherein a timechange of the fluctuation amount is within an allowable range). Thevalidity period (Ts) differs in accordance with fineness (processingaccuracy) of a semiconductor device circuit pattern. In the presentembodiment, the time change amount of the correction value isexperimentally obtained in advance, circuit pattern fineness isclassified into several levels, and allowable periods are registered ina table (901 in FIG. 9). The exposure apparatus can recognizeinformation on fineness based on recipe information previously inputtedin the exposure apparatus or individual information inputted by anoperator. Note that in FIGS. 6A to 6C, the validity period of the imagesurface correction corresponds to a time for exposure processing for 1.5substrates (wafers).

The step-and-scan wafer exposure processing is repeated as waferexposure of the first wafer (step S13). When the wafer exposureprocessing has been completed, it is determined whether or not the nextwafer is to be processed (step S14). If the next wafer is to beprocessed, the process proceeds to step S15. At step S15, the nextexposure processing segment, i.e., a period (time) for the completion ofexposure of the second wafer is prediction-calculated (S602 in FIG. 6B).The time of completion of exposure of the next wafer is expressed asfollows.[next wafer completion time]=[elapsed time(Tr)]+[predicted next waferprocessing time(Tn)]  (Expression 1)

In the present embodiment, it may be arranged such that an (Expression2) where “predicted next wafer processing time (Tn)” in the(Expression 1) is replaced with “first wafer processing time (Tr)” isemployed, thereby prediction accuracy can be increased.[next wafer completion time]=[elapsed time(Tr)]×n   (Expression 2)

Note that in the (Expression 2), “n” indicates that the next wafer isthe n-th wafer.

At step S16, it is determined whether or not processing completion timein the next exposure processing segment is prior to expiration of thecurrently-set validity period of the correction parameter (within thevalidity period). If the processing completion time in the next exposureprocessing segment is within the validity period, the process returns tostep S13, to perform processing in the next exposure processing segment.On the other hand, if the processing completion time in the nextexposure processing segment is not within the validity period, theprocess returns to step S11, to again perform correction valuemeasurement and correction value setting. In the case of FIG. 6B, if thenext wafer completion time does not exceed the validity period (Ts),exposure processing of the second wafer is performed. Thereafter, everytime exposure of one wafer has been completed, it is determined whetheror not the next wafer completion time is prior to the expiration of thevalidity period, and timing, at which measurement of a correctionparameter is required again, is monitored. If the next wafer completiontime exceeds the validity period, it is determined that the validityperiod expires in the middle of exposure of the next wafer. Then,apparatus correction is performed prior to a start of the next waferexposure processing (step S603 in FIG. 6C). At step S603, as in the caseof step S601, the image surface correction value is measured and theconstituent elements (units) are correction-controlled, and using thistime point as a reference time point, measurement of an elapsed time(Tr) is started again.

As described above, in the exposure apparatus of the first embodiment, avalidity period is set in correspondence with a processing accuracy of adevice circuit pattern, and the next correction timing is determinedbased on the validity period. Note that in FIGS. 6A to 6C, exposure ofone wafer is used as the exposure processing segment in FIG. 9, i.e.,whether correction is necessary or not is determined by exposure of onewafer. However, the exposure processing segment may be exposure of N(N≧2) wafers, or exposure for one chip or exposure for one shot.

<Second Embodiment>

In the second embodiment, an operation upon stoppage of exposureprocessing in the exposure processing segment (step S13) in theabove-described first embodiment will be described. In the secondembodiment, upon occurrence of such stoppage, it is determined whetheror not the validity period of the correction value expires if theremaining exposure processing is performed, and the measurement of thecorrection value is performed again in accordance with necessity.

FIGS. 7A to 7C are timing charts showing an apparatus correctionoperation after temporary stoppage of exposure processing, according tothe second embodiment. FIG. 10 is a flowchart showing the apparatuscorrection operation according to the second embodiment. When theprocessing at step S13 in FIG. 9 has been started, first, the processingin the exposure processing segment is started at step S21. Then, if itis determined at step S22 that the processing in the exposure processingsegment has been completed, the processing at step S13 ends. If it isdetermined at step S22 that the exposure processing has not beencompleted, the process proceeds to step S23, at which it is determinedwhether or not a stop instruction has been inputted. If a stopinstruction has not been inputted, the above steps S22 and S23 arerepeated. Then, when a stop instruction is inputted during exposureprocessing, the exposure processing is stopped at step S24 a, and it isdetermined at step S24 b whether or not an instruction to restart theexposure processing has been inputted. The stopped status is maintaineduntil restart is instructed.

When a restart instruction has been inputted, the process proceeds tostep S25, at which the remaining time for the exposure processing to theexposure processing segment is calculated, thereby, the predictedprocessing completion time is calculated. At step S26, it is determinedwhether or not the predicted processing completion time is prior toexpiration of the validity period. If the predicted processingcompletion time is prior to the validity period, the processing isrestarted, and the process returns to step S22. On the other hand, ifthe predicted processing completion time exceeds the validity period,the process proceeds to step S27, to again perform correction valuemeasurement and correction value setting. At step S28, the validityperiod of the correction value is newly set. Note that if the validityperiod set at step S12, is available, it may be used. Then, at step S29,the processing is restarted, and the process returns to step S22.

FIG. 7A shows a status wherein the apparatus has been stopped in themiddle of exposure of the second wafer (S701) after the image surfacecorrection in FIG. 6C. FIG. 7B shows a status wherein the exposureapparatus has been restarted after t seconds. The time of completion ofthe second wafer upon restart of the processing is prediction-calculatedas follows.[current wafer completion time]=[elapsed time(Tr)]+[remaining processingtime(Tn) for 2nd (being processed) wafer]  (Expression 3)

The (Expression 3) may be replaced with an (Expression 4) using thefirst wafer processing time (Tr[1]) and measured stoppage time (t),thereby, the accuracy of prediction of current wafer completion time canbe increased by reflecting a measured value.[current wafer completion time]=[first wafer processingtime(Tr[1])]×n+[stoppage time(t)]  (4)

Note that n indicates that the current wafer is the n-th wafer.

If the current wafer completion time does not exceed the validity period(Ts), the exposure processing is restarted in the middle of the secondwafer. If the current wafer completion time exceeds the validity period(Ts), the apparatus correction is performed as shown in FIG. 7C (S703,S27 and S28). After the execution of the apparatus correction, theexposure processing is restarted in the middle of the second wafer.

<Third Embodiment>

In the first and second embodiments, the validity period is set at stepS12 and step S28 by referring to a table where validity periods areregistered, based on information on circuit pattern fineness. In thethird embodiment, the validity period of the correction parameter isdynamically adjusted. The correction parameter is automatically measuredand corrected while an elapsed time is compared with the validityperiod, as in the case of FIGS. 6A to 6C and FIGS. 7A to 7C in the firstand second embodiments. The difference is that the validity period forthe next correction is determined by calculation based on a predictedcorrection amount and a measured correction amount. That is, correctiontime (validity period) appropriate to an apparatus status can be planned(determined) by not using the experimentally obtained validity period,but feeding back (reflecting) a correction amount measured duringproduction to the determination of a validity period for the nextcorrection time.

Next, an example of feedback of a measured correction amount to the nextvalidity period will be described with reference to FIGS. 8A to 8C. FIG.8A shows a straight line 801 as a time change characteristic of anexperimentally obtained correction value. In this example, a correctionvalue (fluctuation amount) is modeled as a linear function of elapsedtime. Assuming that a fluctuation amount Fth is an allowable limit, theelapsed time Ts to an intersection point 802 between the characteristicline 801 and the fluctuation allowable value Fth is registered as avalidity period.

FIG. 8B shows an example wherein a correction value measured duringproduction is less than a predicted value. When the correction amountmeasured at a point of time Tr1 within the validity period Ts is Fr1, astraight line 804 passing through a point 803 represents acharacteristic of a current apparatus status. Time Ts1, obtained bysubstitution of the limit fluctuation amount Fth into the straight line804, is set as a new validity period. If the measured correction valueis less than the predicted correction value, the next validity period isextended by “Ts1−Ts”.

Next, FIG. 8C shows an example wherein a correction value measuredduring production is greater than a predicted value, in contradiction tothe example in FIG. 8B. In this case, when a correction amount measuredat a point of time Tr2 within the validity period Ts is Fr2, a straightline 806 passing through a point 806 is approximated, and time Ts2,obtained by substitution of the limit fluctuation amount Fth into thestraight line, is set as a new validity period. If the measuredcorrection value is greater than the predicted correction value, thenext validity period is shortened by “Ts−Ts2”.

In FIGS. 8A to 8C, the time change of the correction value is predictedas a linear function. However, it is desirable that correctionparameters based on, e.g., exposure heat as a dominant factor arepredicted as exponential functions. Formulation in such a case can beeasily made.

In the first to third embodiments, the correction planning method in aprojection exposure apparatus has been described. In these embodiments,descriptions have been made regarding one (one type of) correctionparameter, however, the method can be applied to a predeterminedparameter group unit or one parameter unit.

Further, in a case wherein the validity periods are registered inseveral levels corresponding to circuit pattern fineness, if a parameterregarding circuit pattern fineness is set in a recipe (operationparameters) generated by the operator, the validity period of thecorrection parameter can be automatically set based on this parameter.

According to the above embodiments, even for a large number ofcorrection parameters, it is not necessary for the operator to set avalidity period for each of the parameters, and excellent apparatusoperability and productivity can be obtained. Further, even in a casewherein correction must be repeated in a comparatively short period forrequirement of high accuracy, the correction can be performed at anappropriate correction timing based on an apparatus status. Accordingly,unnecessary degradation of productivity in exposure processing can besuppressed while a necessary exposure accuracy can be maintained.

Next, a semiconductor device fabrication process will be described as anexample of fabrication of a micro device, or the like, by utilizing theabove-described exposure apparatus. FIG. 11 is a flowchart showing theflow of an entire semiconductor device fabrication process. At step 1(circuit designing), a semiconductor device circuit pattern is designed.At step 2 (mask fabrication), a mask is fabricated based on the designedpattern.

On the other hand, at step 3 (wafer fabrication), a wafer is fabricatedby using a material such as silicon. At step 4 (wafer process), called apreprocess, an actual circuit is formed on the wafer by a lithographytechnique using the above mask and wafer. At the next step 5 (assembly),called a post process, a semiconductor chip is fabricated by using thewafer carrying the circuit formed at step 4. Step 5 includes an assemblyprocess (dicing and bonding), a packaging process (chip encapsulation),and the like. At step 6 (inspection), inspections such as an operationcheck, a durability test, and the like, are performed on thesemiconductor device formed at step 5. The semiconductor device iscompleted through these processes, and is shipped (step 7).

The wafer process at the above step S4 has an oxidation step ofoxidizing the surface of the wafer, a CVD step of forming an insulatingfilm on the surface of the wafer, an electrode formation step of formingelectrodes by vapor deposition on the wafer, an ion implantation step ofinjecting ions in the wafer, a resist processing step of coating thewafer with a photo resist, an exposure step of exposure-printing thecircuit pattern on the wafer by the above-described exposure apparatus,a development step of developing the exposed wafer, an etching step ofremoving other portions than the developed resist, and a resiststripping step of removing the resist, which is unnecessary after thecompletion of etching. These steps are repeated, to form multiple layersof circuit patterns on the wafer.

According to the present invention as described above, unnecessarydegradation of productivity in exposure processing can be suppressedwhile necessary exposure accuracy can be maintained.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the appended claims.

CLAIM OF PRIORITY

This application claims priority from Japanese Patent Application No.2003-364955 filed on Oct. 24, 2003, the entire contents of which areincorporated by reference herein.

What is claimed is:
 1. A method of exposing a substrate to a pattern using an exposure apparatus, the method comprising: performing an update of a correction parameter, necessary for correction of processing in the exposure apparatus, through measurement of an image formed by the exposure apparatus, the measurement being performed for each update of the parameter; setting a validity time period for the updated correction parameter, the validity time period representing a time period in which the updated correction parameter is valid for the processing; predicting a completion time for a next exposure processing segment to be performed by the exposure apparatus, the completion time being predicted based on a measured processing time for a previous exposure processing segment performed by the exposure apparatus; determining whether the predicted completion time is after expiration of the validity time period, the setting of the validity time period being performed after the performing of the update and before the determining step; causing a further update of the parameter to be performed if it is determined in the determining step that the predicted completion time is after the expiration of the validity time period; and causing a further update to be skipped if it is determined that the predicted completion time is not after the expiration of the validity time period.
 2. A method of manufacturing a device, the method comprising: exposing a substrate to a pattern using an exposure method defined in claim 1; developing the exposed substrate; and processing the developed substrate to manufacture the device.
 3. A method according to claim 1, wherein the completion time is predicted further based on an elapsed time of the processing.
 4. A method according to claim 1, wherein the validity time period is set based on a relation between an elapsed time of the processing and a measured value obtained through the measurement for the correction parameter.
 5. An exposure apparatus for exposing a substrate to a pattern, the apparatus comprising: a measurement device configured to measure an image formed by the exposure apparatus; and a controller configured (i) to perform an update of a correction parameter, necessary for correction of processing in the exposure apparatus, through measurement by the measurement device, the measurement being performed for each update of the parameter, (ii) to set a validity time period for the updated correction parameter, the validity time period representing a time period in which the updated correction parameter is valid for the processing, (iii) to predict a completion time for a next exposure processing segment to be performed by the exposure apparatus, the completion time being predicted based on a measured processing time for a previous exposure processing segment performed by the exposure apparatus, (iv) to determine whether the predicted completion time is after expiration of the validity time period, the setting of the validity time period being performed after the performance of the update and before the determination, (v) to perform the update of the parameter if it is determined that the predicted completion time is after the expiration of the validity time period, and (vi) to skip the update if it is determined that the predicted completion time is not after the expiration of the validity time period.
 6. An apparatus according to claim 5, wherein the controller is configured to set the validity time period based on information which associates an accuracy required for the processing with the validity time period, and information about the accuracy.
 7. An apparatus according to claim 5, wherein the controller is configured to perform the update with respect to each of a plurality of correction parameters, and to set the validity time period with respect to each subset of the plurality of correction parameters.
 8. An apparatus according to claim 5, further comprising a projection optical system configured to project a pattern of a mask to the substrate, wherein the correction parameter corresponds to a position of an image plane of the projection optical system.
 9. An apparatus according to claim 5, wherein the completion time is predicted further based on an elapsed time of the processing.
 10. An apparatus according to claim 5, wherein the validity time period is set based on a relation between an elapsed time of the processing and a measured value obtained through the measurement for the correction parameter.
 11. A method of manufacturing a device, the method comprising: (a) exposing a substrate to a pattern using an exposure apparatus, the apparatus comprising: (i) a measurement device configured to measure an image formed by the exposure apparatus; and (ii) a controller configured (i) to perform an update of a correction parameter, necessary for correction of processing in the exposure apparatus, through measurement by the measurement device, the measurement being performed for each update of the parameter, (ii) to set a validity time period for the updated correction parameter, the validity time period representing a time period in which the updated correction parameter is valid for the processing, (iii) to predict a completion time for a next exposure processing segment to be performed by the exposure apparatus, the completion time being predicted based on a measured processing time for a previous exposure processing segment performed by the exposure apparatus, (iv) to determine whether the predicted completion time is after expiration of the validity time period, the setting of the validity time period being performed after the performance of the update and before the determination, (v) to perform the update of the parameter if it is determined that the predicted completion time is after the expiration of the validity time period, and (vi) to skip the update if it is determined that the predicted completion time is not after the expiration of the validity time period; (b) developing the exposed substrate; and (c) processing the developed substrate to manufacture the device. 